Regulatory functions of serine-46-phosphorylated HPr in Lactococcus lactis.
In: Journal of bacteriology, Jg. 183 (2001-06-01), Heft 11, S. 3391
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Zugriff:
In most low-G+C gram-positive bacteria, the phosphoryl carrier protein HPr of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) becomes phosphorylated at Ser-46. This ATP-dependent reaction is catalyzed by the bifunctional HPr kinase/P-Ser-HPr phosphatase. We found that serine-phosphorylated HPr (P-Ser-HPr) of Lactococcus lactis participates not only in carbon catabolite repression of an operon encoding a beta-glucoside-specific EII and a 6-P-beta-glucosidase but also in inducer exclusion of the non-PTS carbohydrates maltose and ribose. In a wild-type strain, transport of these non-PTS carbohydrates is strongly inhibited by the presence of glucose, whereas in a ptsH1 mutant, in which Ser-46 of HPr is replaced with an alanine, glucose had lost its inhibitory effect. In vitro experiments carried out with L. lactis vesicles had suggested that P-Ser-HPr is also implicated in inducer expulsion of nonmetabolizable homologues of PTS sugars, such as methyl beta-D-thiogalactoside (TMG) and 2-deoxy-D-glucose (2-DG). In vivo experiments with the ptsH1 mutant established that P-Ser-HPr is not necessary for inducer expulsion. Glucose-activated 2-DG expulsion occurred at similar rates in wild-type and ptsH1 mutant strains, whereas TMG expulsion was slowed in the ptsH1 mutant. It therefore seems that P-Ser-HPr is not essential for inducer expulsion but that in certain cases it can play an indirect role in this regulatory process.
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Regulatory functions of serine-46-phosphorylated HPr in Lactococcus lactis.
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Autor/in / Beteiligte Person: | Monedero, V ; Kuipers, OP ; Jamet, E ; Deutscher, J |
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Zeitschrift: | Journal of bacteriology, Jg. 183 (2001-06-01), Heft 11, S. 3391 |
Veröffentlichung: | Washington, DC : American Society for Microbiology, 2001 |
Medientyp: | academicJournal |
ISSN: | 0021-9193 (print) |
DOI: | 10.1128/JB.183.11.3391-3398.2001 |
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